


Swear Jar

by snasational



Series: Old Cherryberry stuff [2]
Category: Undertale (Video Game)
Genre: Dom/sub Undertones, Edging, Established Relationship, Explicit Sexual Content, Fluff and Smut, Light Bondage, M/M, Underfell Sans (Undertale), Underswap Sans (Undertale)
Language: English
Status: Completed
Published: 2020-12-13
Updated: 2020-12-13
Packaged: 2021-03-10 21:14:49
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,993
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28053741
Author URL: https://archiveofourown.org/users/snasational/pseuds/snasational
Summary: Red pulls away and Blue protests. White eye lights meet blue, and the sight of it is enough to quiet Blue’s complaints. “Angel, I wanna try something new.”His soul flutters. “New?”Red nods. “Yeah. I’ve, uh, been thinkin’ about it for awhile now.”
Relationships: CherryBerry, Sans/Sans (Undertale)
Series: Old Cherryberry stuff [2]
Series URL: https://archiveofourown.org/series/2065209
Comments: 2
Kudos: 63





	Swear Jar

**Author's Note:**

> I think maybe i'm getting better at writing???? I still feel a bit rusty but oh well. Also this isn't proofread so forgive me for any mistakes lol
> 
> Red is a bit mean in this one but that's okay because blue is into it.

Five months. They’ve been together for five months, and stuck in Classic’s world for almost a year now. Blue isn’t upset by this, because there’s a possibility that if they get to go home he’ll never see Red again. And really, that’s just not an acceptable end to his relationship. Nothing is, for that matter. 

Five months is a short span of time, all things considered. But it was more than enough to let Blue know that Red was the one for him. It doesn’t matter that they’re technically the same person, because Red belongs to him and he belongs to Red. Just the sight of his smile, all toothy and gold and  _ gorgeous,  _ is enough to make Blue’s soul sing and dance with happiness. 

He loves him so much that it hurts. And, as his brother likes to point out, it’s begun to border on obsession. Blue has never had separation anxiety before, but nowadays going more than a few hours is too much for him to handle. He’ll come back from Grillby’s and find Blue sitting on the couch, waiting up for him no matter how late it is. 

If Red told him it was annoying, Blue would back off. But the thing is, Red acts delighted at this behaviour. He’s not much for words, but his actions say everything. He lets Blue cling and does a fair amount of clinging back. He buys him gifts and trinkets. He helps him come up with riddles. He holds him so close at night that sometimes it feels like their ribcages are going to fuse together.

So if Blue is obsessed, Red is too. 

However, no relationship is perfect (even if his borders on it). The only area that's really been lacking is the sexual aspect. He often feels like Red is holding back on him and it’s irritating to no end. Blue isn’t a virgin anymore! There’s no need to be overly gentle with him! Red knows for a fact that Blue can take being roughened up, and yet he insists on treating him with the utmost care.

At first it was flattering. Now it’s making him want to punch a wall. Yes, the sex is amazing! That doesn’t mean it has to be so... _ plain _ . 

Admittedly, Blue wasn’t the most knowledgeable on sex prior to meeting Red. He knew the basics, of course, but learning the fine print to it didn’t interest him all that much. It was Red who taught him the lingo, and where to put your hands, and how to feel like you’re on cloud nine. But he began his own research, and started learning about all of the different kinds of things you can do while having sex. 

And while some of the things he’s seen are intimidating, he wants Red to know that he’s open to anything. They don’t have to stick to being plain!

The really complicated part to this whole ordeal is actually telling Red how he feels. The last thing he wants to do is offend him, Blue would feel so guilty at the implication that Red can’t properly satisfy him that he might actually die. They don’t even have to have sex to make Blue happy because Red will always be enough for him. 

As it turns out, luck is on his side. 

They’re kissing like they always do before bed. It’s Blue’s favorite type of kiss, the kind that makes him feel hot and draws out wonderful noises from Red. His boyfriend’s hands are rubbing at his shoulder blades, and Blue has his own bunched up at the collar of Red’s jacket. It’s perfect.

Red pulls away and Blue protests. White eye lights meet blue, and the sight of it is enough to quiet Blue’s complaints. “Angel, I wanna try something new.” 

His soul flutters. “New?”

Red nods. “Yeah. I’ve, uh, been thinkin’ about it for awhile now.”

With no hesitation whatsoever, Blue agrees. “Yes! Yes, we can try it. Anything you want.”

His partner snorts and clacks their foreheads together affectionately. “You bonehead, I didn’t even tell you what I wanted to do.” 

“Then make it a surprise.” 

Red sighs, sounding entirely like the lovestruck fool he is. “Man, what did I do to deserve you? Alright angel, close your eyes and lay back for me.”

Blue is more than happy to comply. As he’s situating himself on their pillows, he hears the slide of leather being pulled through metal. Blue shudders at the sound of it but doesn’t do anything to stop him, nor does he disobey his orders by opening his eyes. And then he’s pulling his arms together and tying them together. 

“Good.” Red says with a pleased tone. “You can open your eyes now.” 

He’s greeted with the sight of Red now collarless. Blue sucks in a breath when he sees the bare bone of his neck, unchipped and smooth.That’s probably thanks to the collar. Blue supposes he should be grateful that it has protected his beloved from being marred, but truthfully the damned thing fills Blue up with a bitter jealousy that he’s never felt before. 

Red doesn’t like talking about the collar, and Blue figures he’ll come clean about it when he’s ready. 

For now, however, the collar is currently wrapped around Blue’s wrists. He thinks this is called ‘bondage’, albeit a little more tamer than what this world’s Alphys had told him about. 

“Wowzers.” Blue breathes out. “Yeah, this is certainly new.”

Red chuckles. “This ain’t it, but...i’ll just let you figure it out on your own. If you want me to stop, just say...uh, jar.”

“Jar?” Blue giggles. “Okay! I can do that.” 

Red gives him a fond grin before setting to work. There’s not much left to do, since lately they’ve both been going to bed shirtless. It makes their nightly activities more convenient, and Blue doesn’t want anymore of his perfectly good t-shirts ruined. Pretty soon the both of them are naked, thanks to Red’s handy work. 

“God, you’re so hot.”

“Don’t we have the same body?” Blue teases, but nonetheless his bones flush at the crude compliment. 

“Yeah, and I’m pretty fucking hot too.” He winks. 

“That-  _ oh.”  _ He’s cut off when Red begins licking one of his floating ribs. By now, Red knows every single sensitive spot on his body. The tenderness in the way he curls his tongue around his sensitive bones is soul melting. Every wet slide feels appreciative, like Blue is a God and Red is a devoted servant worshiping him. 

“You taste so good.” He murmurs against his spine. “Fuck, I could do this all day.”

Blue responds with a whimper. It’s the tone of voice that gets him. Every single time, without fail. The deep rumble, so much like his own voice but at the same entirely different. Red’s voice is best compared to a cat with a really deep purr. Okay,  _ maybe  _ Blue isn’t the best at coming up with analogies. He’ll leave that to Classic and Papy. 

His magic swirls until a cock is formed. But it doesn’t stop there. The magic moves and swallows his femurs and pelvis, creating a soft blue form that almost resembles human anatomy. This development isn’t a new one, especially when it comes to making female parts, but it’s still one that Blue isn’t used to in the slightest. Red loves it when he does this, says that it gives him more to grab onto while he’s railing him. 

Blue would prefer terms like ‘making love’ but Red’s not romantic enough for that. And, as much as Blue likes to pretend he’s a romantic at heart, there’s something about the blunt way Red says things that makes him hornier than he ever thought possible.    
  


Usually, he’d be grabbing onto something, but his tied hands leaves him unable to do anything but squirm on the bed. The way Red is touching him is driving him crazy, and his dick hasn’t even been spared so much as a glance yet. 

“Look at you,” His lover purrs. He kneads his hands into Blue’s hips. “You’re leaking everywhere. Don’t even need a cunt to get wet for me, do you?” 

“Hnn,  _ Red.”  _ Blue pants. Red seems to get the hint, because boney fingers are finally being wrapped around his dick in a loose grip. He gives it a few strokes, enjoying the way more beads of precum well up at the action. Blue’s dick doesn’t usually get attention so the slightest of touches has him trembling. 

Despite this, it’s not enough. “Please.”

“Use your words angel. Please  _ what _ ?”

Blue gasps when a thumb swipes over his slit. “Please! Go faster!” 

“That’s more like it.” With an expert hand, Red readjusts and grip and begins to pump Blue cock fast and hard. It’s the way he likes to do himself, and from the way Blue has begun to moan and squirm, he figures his hypothesis is correct. 

The build up is fast. His magic coils inside his groin, begging for release. With every flick of Red’s wrist it builds up more and more, until it’s ready to explode. He lets out a sob and arches his spine, chasing release. It’s so close, Blue can practically taste it. “Yes! Oh, oh, I’m-”

Red let’s go of his cock and Blue is suddenly thrusting into the air. His eye sockets fly open and his mouth drops in displeasure. Red is looking down at him with an edge to his smirk, like ruining his orgasm was one hundred percent his intention. 

“Red!” Blue chokes. 

“Shh,” Red hushes, caressing his phalanges down the soft magic that makes up Blue’s thighs.  They’re trembling so hard that it rattles Blue’s ribcage. “It’s alright angel, just relax.”

Blue lets out a whine. If he could, he’d close his thighs together but Red’s body prevents that from happening. “I-I n-need to, Red, p-please.  _ Please _ .” 

“You will,” Red assures. “I promise. You trust me, don’t you?” 

He nods earnestly. Red softens at this.

“Good boy.” 

Red slides down Blue’s body, kissing wherever his teeth touch until he reaches Blue’s cock. It twitches sporadically, a sign of his desperation to cum. Feeling that heated gaze on his cock makes it give a particularly hard twitch, and with it comes a large string of precum that oozes down the side. Perhaps it should be a disgusting sight, but it only makes Red’s magic water. 

He leans forward and laps up the mess that Blue made. The taste is mild, but Red can’t get enough of it. He sucks and nibbles and licks every inch of Blue’s cock until the only fluid left on him is Red’s magic. At some point he has to hold down Blue’s hips to stop him from squirming, which is punished by a sharp nip where the base of his cock meets his groin. 

It’s not enough to puncture the magic, but it’s enough for Blue to freeze and hold as still as possible. Red strokes that mark apologetically. He doesn’t linger on it for too long, and gets right back to working on Blue’s dick. After he’s satisfied enough with his clean up job, he grips the cock harder and swallows it whole. This elicits a loud cry from Blue, and despite his best attempts his hips still stutter. 

“Oh,” He sighs. “It feels  _ so  _ good Red.” The pressure is back much quicker. Just a little more, and he-

Red pulls his mouth away. Blue actually does start crying this time. 

“Fuck!” He sobs, not even bothering to stop the way his hips thrust into nothingness. “Fucking, please! Fuck me, fuck me, fuck me, please, let me cum,  _ please _ !” He doesn’t even notice the vulgarity of his words, too fogged up over yet another cut off. But Red does, and it draws out a dark chuckle from him. 

“Aww,” He cooes. It’s malicious, and there’s a sharpness to his voice that makes Blue’s soul flutter. If Red talked to him like that outside of sex he’d probably cry. “There there, dry up them tears. You’re okay. Let me tell you something, angel.” 

He crawls forward again, his pussy hovering over Blue’s cock. “You don’t get to cum unless I tell you too.” The tone of voice leaves no argument. “Understood?”

Blue nods shakily. Red growls. He gives a reprimanding swat to Blue’s thigh. He yelps at this and whimpers at the accompanying sting. “Use them words of yours, angel.”

“Y-yes.” He sniffles, more tears flowing from his eye sockets. 

Red is apparently happy with him, because as he’s sinking down onto Blue’s cock he bends forward and licks away his partner’s tears. He cups Blue’s face in the palms of his hands and nuzzles their foreheads together while he bottoms out. It’s loving and tender, the exact opposite of how he was treating him before. 

“You fill me up so nicely, angel. Like you were made to fit me and only me.” 

He can only moan in response, lost in the sensation of tight magic hugging his cock. They’ve only done this once, because Red has a preference using his dick. Blue doesn’t mind what they do as long as it makes Red happy. Still, he certainly won’t be complaining if this becomes a new normal even if he does love the way Red fucks him. 

Red squeezes his chubby thighs over Blue’s hips. It’s his only warning before Red lets go of him and leans back. He braces his hands on the bed and begins to roll his hips. It sets a steady tempo. Blue almost expected it to be rough and fast, the way he knows Red likes. He’s fine with this, though. When they go slow, he gets to feel every single pull and drag of Red, and it makes his nerves go haywire. 

“Oh fuck, Red!” He groans. This time, he arches his hips up to meet Red’s shallow thrust. It pulls a gasp out of him, and then a snarl. 

“Did I say you could move again?” He hisses, his hips stopping their movement. 

“B-but-” Another swat at his thigh, harder than the last one. Blue chokes back a sob. 

“ _ Bad _ .” Red’s eye socket turns scarlet, and Blue realizes what’s happening a tad bit too late. His soul is encircled with magic, freezing him to the spot. “Now you don’t have any choice but to listen to me.” 

“I’m sorry.” Blue mewls. “Please, I won’t do it again.” 

Red doesn’t respond. Instead, he picks up his pace until he’s practically bouncing on Blue’s cock. He can’t thrash, or thrust, or arch his spine, so all he’s left to do is take his lover’s brutal rythme. It’s like he’s a toy for Red to use, and the thought of that is more appealing than he would’ve previously thought. 

Red moves one of his hands and rubs his clit. “Fuck,” he draws out. “Can’t stop looking at you. Crying for me, begging for me, you’re so perfect.” His pussy spasms around Blue’s cock. “I bet you’d let me do this for  _ hours.  _ You’re a good boy like that, you take such good care of me angel.”

A gush of wetness drowns Blue’s cock, and the spasmings increase tenfold. It’s both heaven and torture, but Red’s words echo in his head. No cumming until he says so, and Blue has already disobeyed him one too many times. He wants to make Red proud, so he holds back even if it burns. 

Red keens, a noise Blue has never heard from him before. “Holy  _ shit _ .” 

Suddenly, he releases his magic and Blue is able to move again. He couldn’t stop the way his hips move if he wanted too. The need to cum has completely overcome every logical thought process and has reduced him to nothing more than a drooling, pleading mess. The tears fall freely, making a mess out of his face. 

He doesn’t register the fact that his hands have been untied until they’re gripping plump hips. “Come on, you’ve been so good for me. Fill me up.” 

He blacks out at the force of his orgasm, strong after being delayed for so long. The world spins, and all he can think about is how much he loves Red.

*

When he wakes up, his pants are back on and his bones feel like they’ve been wiped down recently. Their comforter is piled on top of him, encasing him in comfortable warmth. “Red?” He calls out, concerned by the lack of cuddling going on. 

“Right here.” The voice comes from beside him. Blue rolls over in his cocoon and is met with Red sitting up. He looks...guilty?

“Are you okay?” He asks, concerned. Red doesn’t meet his eyes. Instead, they’re trained on the chipped paint of their walls. 

“I didn’t hurt you, did I?” 

Oh. Blue gets it now. “No! You were the absolute bestest!”

He looks disbelieving, and Blue just can’t have that. He squirms out of his blankets and wraps his arms around Red’s shoulders, pulling him close. 

“I mean it Red! If I didn’t want something to happen I would’ve said the word. I pinky promise, you did nothing wrong. In fact, the Magnificent Sans hasn’t felt this pleased in a long time.” He rubs his shoulder blades comfortingly. 

Red snorts. He’s always deeply amused by the ‘Magnificent Sans’ bit Blue likes to do. “Well, since we’re pinky promising, I guess I ain’t got no other choice but to believe you.” 

Blue grins. 

“By the way, that’s gunna be 6G in the jar. Don’t think I forgot about them nasty words coming out of that pretty little mouth of yours.” 

He flushes. “I don’t know what you’re talking about.”

*

“You know, Stretch. The Great Papyrus thinks that perhaps we should move them into the shed.” Puff tells his counterpart after yet another night of no sleep. Stretch merely groans into the pillow that's wrapped over his cranium. 

**Author's Note:**

> i don't know the ship name for UT pap/US pap. HoneyPuff????? Oh well, expect to see them feature in these little fics at some point. 
> 
> Twitter is @ askeletonthot
> 
> Comments & Kudos are always appreciated!!


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